[Plugin: All-in-One Event Calendar] Blank event detail page

as an alternative to all-in-calendar you can try – https://www.ads-software.com/extend/plugins/calpress-event-calendar/

This is because you are using a custom theme!

To solve this, you need to create a ai1ec-event specific page render type.

In your theme directory, create a new file “single-ai1ec_event.php”, with the following contents (taken from Twenty Eleven):

<?php
/**
 * The Template for displaying all single posts.
 *
 * @package WordPress
 * @subpackage Twenty_Eleven
 * @since Twenty Eleven 1.0
 */

get_header(); ?>

		<div id="primary">
			<div id="content" role="main">

				<?php while ( have_posts() ) : the_post(); ?>

					<nav id="nav-single">
						<h3 class="assistive-text"><?php _e( 'Post navigation', 'twentyeleven' ); ?></h3>
						<span class="nav-previous"><?php previous_post_link( '%link', __( '<span class="meta-nav">←</span> Previous', 'twentyeleven' ) ); ?></span>
						<span class="nav-next"><?php next_post_link( '%link', __( 'Next <span class="meta-nav">→</span>', 'twentyeleven' ) ); ?></span>
					</nav><!-- #nav-single -->

<?php
/**
 * The template for displaying content in the single.php template
 *
 * @package WordPress
 * @subpackage Twenty_Eleven
 * @since Twenty Eleven 1.0
 */
?>

<article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>
	<header class="entry-header">
		<h1 class="entry-title"><?php the_title(); ?></h1>

		<?php if ( 'post' == get_post_type() ) : ?>
		<div class="entry-meta">
			<?php twentyeleven_posted_on(); ?>
		</div><!-- .entry-meta -->
		<?php endif; ?>
	</header><!-- .entry-header -->

	<div class="entry-content">
		<?php the_content(); ?>
		<?php wp_link_pages( array( 'before' => '<div class="page-link"><span>' . __( 'Pages:', 'twentyeleven' ) . '</span>', 'after' => '</div>' ) ); ?>
	</div><!-- .entry-content -->

	<footer class="entry-meta">
		<?php
			/* translators: used between list items, there is a space after the comma */
			$categories_list = get_the_category_list( __( ', ', 'twentyeleven' ) );

			/* translators: used between list items, there is a space after the comma */
			$tag_list = get_the_tag_list( '', __( ', ', 'twentyeleven' ) );
			if ( '' != $tag_list ) {
				$utility_text = __( 'This entry was posted in %1$s and tagged %2$s by <a href="%6$s">%5$s</a>. Bookmark the <a href="%3$s" title="Permalink to %4$s" rel="bookmark">permalink</a>.', 'twentyeleven' );
			} elseif ( '' != $categories_list ) {
				$utility_text = __( 'This entry was posted in %1$s by <a href="%6$s">%5$s</a>. Bookmark the <a href="%3$s" title="Permalink to %4$s" rel="bookmark">permalink</a>.', 'twentyeleven' );
			} else {
				$utility_text = __( 'This entry was posted by <a href="%6$s">%5$s</a>. Bookmark the <a href="%3$s" title="Permalink to %4$s" rel="bookmark">permalink</a>.', 'twentyeleven' );
			}

			printf(
				$utility_text,
				$categories_list,
				$tag_list,
				esc_url( get_permalink() ),
				the_title_attribute( 'echo=0' ),
				get_the_author(),
				esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) )
			);
		?>
		<?php edit_post_link( __( 'Edit', 'twentyeleven' ), '<span class="edit-link">', '</span>' ); ?>

		<?php if ( get_the_author_meta( 'description' ) && ( ! function_exists( 'is_multi_author' ) || is_multi_author() ) ) : // If a user has filled out their description and this is a multi-author blog, show a bio on their entries ?>
		<div id="author-info">
			<div id="author-avatar">
				<?php echo get_avatar( get_the_author_meta( 'user_email' ), apply_filters( 'twentyeleven_author_bio_avatar_size', 68 ) ); ?>
			</div><!-- #author-avatar -->
			<div id="author-description">
				<h2><?php printf( __( 'About %s', 'twentyeleven' ), get_the_author() ); ?></h2>
				<?php the_author_meta( 'description' ); ?>
				<div id="author-link">
					<a>" rel="author">
						<?php printf( __( 'View all posts by %s <span class="meta-nav">→</span>', 'twentyeleven' ), get_the_author() ); ?>
					</a>
				</div><!-- #author-link	-->
			</div><!-- #author-description -->
		</div><!-- #entry-author-info -->
		<?php endif; ?>
	</footer><!-- .entry-meta -->
</article><!-- #post-<?php the_ID(); ?> -->

					<?php comments_template( '', true ); ?>

				<?php endwhile; // end of the loop. ?>

			</div><!-- #content -->
		</div><!-- #primary -->

<?php get_footer(); ?>

Now refresh the page.

If you see the event contents, then it is verified that it is a problem with your custom theme. You will need to slowly modify the file by copying blocks of your original theme’s single-post render type (“single.php”).